1. Field of the Invention
The present invention relates to a tape loading apparatus suitably applied to a mgnetic recording/reproducing apparatus such as a cassette-type video tape recorder and, more particularly, to a tape loading apparatus for extracting a tape from a tape cassette by a pair of tape guide blocks which are moved along both sides of a rotary head drum so as to helically wind the tape around the rotary head drum in a substantially .OMEGA.-shaped manner.
2. Description of the Prior Art
The present inventor has examined a conventional tape loading apparatus shown in FIGS. 1 to 3 to devise the present invention.
In this conventional tape loading apparatus, a magnetic tape (hereinafter, described only as "tape" for brevity) 5 is extracted from a tape cassette 4 by a pair of tape guide blocks (hereinafter, each described only as "guide block") 2 and 3 which can be moved along both sides, of a rotary head drum (hereinafter, described only as "drum") 1. The extracted tape is helically wound around the outer surface of the drum 1 for an angular interval of nearly 360.degree. in a substantially .OMEGA.-shaped manner.
The specific construction of this tape loading apparatus will be described.
Each of the pair of guide blocks 2 and 3 comprises a tape guide 8 constituted by a fixed pin and a pair of tape guides 9 and 10 constituted by rollers. The tape guides 8, 9 and 10 are mounted on a corresponding carrier 7 in a triangular arrangement as shown in FIG. 1.
The drum 1 is vertically mounted on a chassis 11. A pair of guide rails 12 and 13 are disposed around both sides of the drum 1 to guide the guide blocks 2 and 3, respectively. The guide rails 12 and 13 comprise substantially J-shaped plates arcuated along the outer circumference of the drum 1 and are arranged symmetrically with each other about the drum 1. Guide grooves 14 are formed at the central portions of the guide rails 12 and 13 along their longitudinal directions. The guide blocks 2 and 3 are placed on the guide rails 12 and 13 through the carriers 7, respectively. A pair of guide pins 15 and 16 are fixed on the lower surface of each carrier 7 at positions spaced apart from each other and they are fitted in the corresponding one of guide grooves 14. Therefore, the guide blocks 2 and 3 are slidably guided by the guide grooves 14 of the guide rails 12 and 13, respectively. In particular, the guide blocks 2 and 3 can be moved along both sides of the drum 1 between the original positions indicated by imaginary lines in FIGS. 1 and 2 and tape-loaded positions indicated by solid lines in FIGS. 1 and 2.
A pair of upper and lower ring gears 18 and 19 are rotatably supported by the chassis 11 around the outer circumference of the lower portion of the drum 1 and are parallel to each other in horizontal planes perpendicular to the axis of the drum 1. The upper and lower ring gears 18 and 19 have outer gear portions 20. Drive gear mechanisms 23 and 24 each comprises a gear 21 engaged with the corresponding gear portion 20 and a worm wheel 22 fixedly connected to the gear 21 by a shaft. In particular, the drive gear mechanisms 23 and 24 are disposed on the chassis 11 such that the upper ring gear 18 meshes with the gear 21 of the drive gear mechanism 23, and the lower ring gear 19 meshes with the gear 21 of the drive gear mechanism 22. The worm wheels 22 of the drive gear mechanisms 23 and 24 mesh with both sides of a worm 27 attached to the motor shaft 26 of a drive motor 25 which is mounted on the chassis 11.
When the guide blocks 2 and 3 are located at the original positions, respectively, the tape guides 8, 9 and 10 of these guide blocks 2 and 3 are at the same level as that of the tape 5 in the tape cassette 4, as shown in FIG. 2. On the other hand, when the guide blocks 2 and 3 are moved to the tape-loaded positions, respectively, the tape guides 8, 9 and 10 of the guide block 2 are at a different level from those of the guide block 3 with respect to the axial direction of the drum 1, as shown in FIG. 3. More specifically, in the tape-loaded positions, the tape guides 8, 9 and 10 of the guide block 2 are at a higher level than that of the tape 5 in the tape cassette 4 and the tape guides 8, 9 and 10 of the guide block 3 are at a lower level than that of the tape 5 in the tape cassette 4. Therefore, the guide rail 12 is inclined upward from the original position to the tape-loaded position of the guide block 2 with respect to the horizontal plane. On the other hand, the guide rail 13 is inclined downward from the original position to the tape-loaded position of the guide block 3 with respect to the horizontal plane. It should be noted that the guide rails 12 and 13 have inclined angles corresponding to that of a helical tape lead 1a formed on the outer circumference of the drum 1.
The guide blocks 2 and 3 are connected to the upper and lower ring gears 18 and 19 through links 29 and 30, respectively. The links 29 and 30 are each arcuately shaped. Front end portions 29a and 30a of the links 29 and 30 engage with pins 32 fitted in arcuate holes 31 formed in the upper and lower ring gears 18 and 19, respectively. Rear end portions 29b and 30b of the links 29 and 30 are bent upwardly into channel shapes and engage with the lower end portions of the guide pins 15 of the guide blocks 2 and 3, respectively. The rear end portion 30b of the link 30 bypasses the upper ring gear 18. Tension springs 34 and 35 are disposed between the front end portions 29a and 30a of the links 29 and 30 and spring stop holes 33 formed in the front sides of the elongated holes 31 of the ring gears 18 and 19, respectively.
In the tape loading apparatus having the construction described above, when the tape cassette 4 is loaded at the cassette loading position shown in FIG. 2, the tape guides 8, 9 and 10 of the guide blocks 2 and 3 located in the original positions are relatively inserted to positions inside the tape 5 of the tape cassette 4, as indicated by imaginary lines in FIGS. 1 and 2. When loading of the tape cassette 4 is completed, the drive motor 25 is automatically driven to rotate in the forward or normal direction, thereby starting the loading operation of the tape 5.
When the motor 25 rotates in the normal direction, the worm wheels 22 of the drive gear mechanisms 23 and 24 are rotated by the worm 27 in the opposite directions to each other. The gears 21 of the drive gear mechanisms 23 and 24 drive the ring gears 18 and 19 though the outer gear portions 20 thereof, respectively. The ring gears 18 and 19 are rotated in the opposite directions as indicated by arrows a and b. As a result, the ring gears 18 and 19 pull the links 29 and 30 through the tension springs 34 and 35 in the directions indicated by the arrows a and b, respectively, so that the links 29 and 30 pull the guide pins 15 of the guide blocks 2 and 3, respectively.
The guide blocks 2 and 3 are slid in the guide grooves 14 along the guide rails 12 and 13 from the original positions in the directions, indicated by arrows c and d, respectively. As a result, the tape guides 8, 9 and 10 of the guide blocks 2 and 3 extract the tape 5 from the tape cassette 4 toward both sides of the drum 1. The guide block 2 is gradually moved upward along the inclined curve of the guide rail 12 with respect to the horizontal plane while the guide block 3 is gradually moved downward along the inclined curve of the guide rail 13 with respect to the horizontal plane, as shown in FIG. 2. The extracted tape 5 is gradually wound (loaded) around the outer circumference of the drum 1 in a substantially .OMEGA.-shaped manner. In this time, since inclined angles of the guide rails 12 and 13 correspond to that of the helical tape lead 1a with respect to the horizontal plane, the tape guides 8, 9 and 10 of the guide blocks 2 and 3 are moved along ideal loci corresponding to the helical tape lead 1a. As a result, the tape 5 is ideally loaded around the drum 1 along the tape lead 1a.
When the guide blocks 2 and 3 reach the tape-loaded positions, respectively, index pins 37 and 38 fixed on the guide rails 12 and 13 are engaged with V-shaped grooves 39 formed at the front ends of the carriers 7, respectively. The guide blocks 2 and 3 are then stopped by the index pins 37 and 38 from being pulled by the tension springs 34 and 35, respectively. At the same time, the drive motor 25 is stopped. Thereby, the stop positions of the ring gears 18 and 19 are defined by the self-lock function between the worm 27 and the worm wheels 22. As a result, the tensions of the springs 34 and 35 that press the guide blocks 2 and 3 onto the index pins 37 and 38, respectively, are regulated.
When the guide blocks 2 and 3 are positioned in the tape-loaded positions, as shown in FIG. 3, they are at different levels with respect to the axial direction of the drum 1. As shown in FIG. 1, the tape 5 is helically wound around the drum 1 for an angular interval of nerely 360.degree. along the tape lead 1a in a substantially .OMEGA.-shaped manner, thereby completing the tape loading operation.
It should be noted that the extensions of the tape 5 from the guide blocks 2 and 3 to both sides thereof, as shown in FIG. 1, are performed by tension levers (not shown). It should also be noted that the tape 5 is unloaded by rotating the drive motor 25 in the reverse direction in accordance with the reverse procedures to those in the above-mentioned tape loading operation.
However, this conventional tape loading apparatus has the following drawbacks:
(1) In the tape loading operation, the ring gears 18 and 19 are rotated parallel to the horizontal plane, but the guide blocks 2 and 3 are gradually guided upward and downward along the helical tape lead 1a of the drum 1. Thus, the positional relationships in the vertical direction between the ring gears 18 and 19 and the guide blocks 2 and 3 are gradually changed, respectively, and not maintained constant. The level difference between the guide blocks 2 and 3 in the tape-loaded positions must be achieved with use of the links 29 and 30 which connect the guide blocks 2 and 3 to the ring gears 18 and 19, respectively. Therefore, the links 29 and 30 must be pivoted upward and downward at the engaging portions with the engaging pins 32 of the ring gears 18 and 19 and the guide pins 15 of the guide blocks 2 and 3, respectively. As a result, the links 29 and 30 are undesirably stressed. As a result, a considerable difference occurs in the drive forces respectively transmitted from the ring gears 18 and 19 to the guide blocks 2 and 3 through the links 29 and 30. The guide blocks 2 and 3 cannot then be smoothly driven with substantially the same drive force. In addition, a considerable difference also occurs between the forces for pressing the guide blocks 2 and 3 to the index pins 37 and 38 at the tape-loaded positions by means of the elongations of the tension springs 37 and 38 as previously described. When such difference between the pressing forces occurs, the tightening force of the tape 5 onto the drum 1 by the tape guides 8 of the guide blocks 2 and 3 becomes unstable, so the prescribed tightening force cannot be obtained. The tape guides 8 become unsteady during tape travel, so the tape travel becomes unstable. As a result, the recording/reproducing precision is degraded.
(2) Since the relationships between the levels of the ring gears 18 and 19 and the guide blocks 2 and 3 cannot be kept constant during the tape loading operation, the loads acting on the ring gears 18 and 19 become nonuniform. As a result, a problem occurs in the driving of the ring gears 18 and 19 by means of the drive motor 25.
(3) During the tape loading operation, the links 29 and 30 must be pivoted upward and downward with respect to engaging pins 32 of the ring gears 18 and 19 and the guide pins 15 of the guide blocks 2 and 3 as previously described. For this purpose, special hinge structures must be provided to prevent the end portions 29a and 30a of the links 29 and 30 from being vertically removed from the engaging pins 32 and the end portions 29b and 30b of the links 29 and 30 from the guide pins 15 such that the links 29 and 30 can pivot vertically. However, when the end portions 29a and 30a and 29b and 30b of the links 29 and 30 are connected to the engaging pins 32 and the guide pins 16 through such special hinge structures as described above, the assembly operation becomes troublesome. In particular, repair of the apparatus becomes complicated and time-consuming, for example, when the guide rails 12 and 13 have to be replaced.
In order to overcome the conventional drawbacks (1) to (3), the present inventor has examined a tape loading apparatus shown in FIG. 4.
In this case, a ring gear 18 is inclined upward with respect to the horizontal plane and a ring gear 19 is inclined downward with respect to the horizontal plane.
However, the guide rails 12 and 13 are inclined along the helical tape lead of the drum 1 but it is impossible that the inclinations of the ring gears 18 and 19 are completely matched to that of the helical tape lead. In addition to this disadvantage, since the ring gears 18 and 19 are inclined upward and downward with respect to the horizontal plane, drive gear mechanisms 23 and 24 must also be inclined in the opposite directions to each other. As a result, support mechanisms for the ring gears 18 and 19 and the drive gear mechanisms 23 and 24 become very complex, resulting in high cost.